Wavelength-selective switches (WSSs) are of utmost importance for optical networking, for implementing reconfigurable optical add/drop multiplexers (ROADM) and path switching in mesh networking. WSS have been demonstrated in planar lightwave circuits (PLC) typically using thermooptic switching, in free-space optics using MEMS micromirror switching, and in some hybrid configurations mixing PLC and MEMS technology. PLC is advantageous due to its form factor (flat packaging) and robustness whereas MEMS micromirror switching is advantageous for its low power consumption, multistate switching states, and high extinction. Combining the two technologies directly is hindered by the fact that MEMS micromirrors actuate in free-space, in contrast to the PLC where light is guided in some higher index solid material. Recently a rotating, solid-immersion mirror design (FIG. 1) has been proposed and demonstrated within the guiding PLC (see “Solid-Immersion Micromirror with Enhanced Angular Deflection for Silcon-Based Planar Lightwave Circuits” by C-H. Chi et al, published in Proc. of Optical MEMS, August 2005). The solid-immersion micromirror 110 (the rotating portion that includes the mirror 111) is separated by a curved air gap 112 from the remaining guiding PLC 113. The air gap separation equals a quarter of a wavelength of the guided light (or additional increments of half-wavelength). Hence the reflections from the interfaces between the two guided regions 110, 113 and the air gap 112 destructively interfere. The mirror 111 is formed by etching into the rotating portion 110 and metalizing the surface, or by creating a Bragg mirror structure using the guided material 110 and air.
However, while this solid-immersion micromirror (SIM) arrangement provides improved deflection and reduced diffraction loss, it needs to be integrated with additional structures on the PLC in order to construct a WSS. Other attempts of integrating MEMS mirrors (non-immersion type) with PLCs to construct WSSs have been reported, using piston actuation (D. T. Fuchs, et al, “A hybrid MEMS-waveguide wavelength selective cross-connect,” Photon Technol Lett 16, pp. 99-101, 2004) and tilting mirrors (C. H. Chi et al, “Integrated 1×4 WSS with on-chip MEMS mirrors,” CLEO 05, Baltimore, Md., “CLEO 05). What is needed is a way to fully integrate the SIM unit together with the PLC to form a planar wavelength-selective switch (WSS).